Guide To UNIX Using Linux Third Edition Chapter One The Essence of UNIX and Linux Guide To UNIX Using Linux Third Edition

Objectives Explain operating systems, including PC, mainframe, and network operating systems Describe the UNIX and Linux operating systems Explain the purpose of UNIX/Linux shells Understand how to select user names and passwords Connect to UNIX/Linux using Telnet or SSH Guide to UNIX Using Linux, Third Edition

Objectives (continued) Use basic UNIX/Linux commands and command-line editing features Explain the role of a system administrator Change your password for security Use multiple commands to view the contents of files Redirect output to a file Guide to UNIX Using Linux, Third Edition

Understanding Operating Systems Operating System (OS) The most fundamental computer program Enables you to store information, process raw data, use application software, compile your own programs, and access attached hardware, such as a printer or keyboard Guide to UNIX Using Linux, Third Edition

Understanding Operating Systems Guide to UNIX Using Linux, Third Edition

PC Operating Systems A personal computer (PC) OS conducts all I/O, processing, and storage operations on a stand-alone computer Guide to UNIX Using Linux, Third Edition

Mainframe Operating Systems A mainframe OS controls a large computer system with multiple processors for I/O, processing, and storage operations for many users Guide to UNIX Using Linux, Third Edition

Network Operating Systems A network OS controls the operations of a server computer (host), which accepts requests from user programs running on other computers (clients) Guide to UNIX Using Linux, Third Edition

Server-based vs. peer-to-peer networks Server-based network Centralized processing approach Data and applications server resident If server fails, entire network fails Peer-to-peer Distributed processing approach Data and applications workstation resident Each system is both a server and a client Guide to UNIX Using Linux, Third Edition

Introducing the UNIX and Linux Operating Systems UNIX/Linux can be used on systems functioning as: Dedicated servers or client workstations in a server-based network Client/server workstations connected to a peer-to-peer network Stand-alone workstations not connected to a network Guide to UNIX Using Linux, Third Edition

Introducing the UNIX and Linux Operating Systems (continued) UNIX/Linux is a multi-user system UNIX/Linux is a multitasking system Can execute more than one program at a time UNIX/Linux is a portable operating system Used in many computing environments Guide to UNIX Using Linux, Third Edition

A Brief History of UNIX Bell Labs originally developed UNIX in the late 1960s and early 1970s Distributed in source code form Universities modified the code to work on different machines Two standard versions of UNIX evolved System V (Bell Labs) Berkeley Software Distribution (BSD) Guide to UNIX Using Linux, Third Edition

UNIX Concepts Shell The interface between user and OS Hierarchical Structure Directory and subdirectory organization Layered components Layers of software surround the computer’s inner core Guide to UNIX Using Linux, Third Edition

Guide to UNIX Using Linux, Third Edition

Linux and UNIX Linux is UNIX-like Not written from traditional UNIX code Linux is original code Includes POSIX standards Other Linux information Created by Linus Torvalds Offers all the complexity of UNIX Linux can coexist with other OSs Guide to UNIX Using Linux, Third Edition

Introducing UNIX/Linux Shells A shell is a UNIX/Linux program that interprets the commands you enter from the keyboard Guide to UNIX Using Linux, Third Edition

Choosing Your Shell Shells interpret commands and act as first-class programming languages A default shell is associated with your account when created; Bash is the default shell in Linux Some UNIX/Linux shells: Bourne, Korn, C shell, Bash Can switch from shell to shell Guide to UNIX Using Linux, Third Edition

Choosing User Names and Passwords To use UNIX/Linux, a user must log in by providing a unique user name and password UNIX/Linux system administrators create accounts by adding user names and passwords Users log in to UNIX or Linux systems as long as they have accounts on the workstation or host (server) computer Guide to UNIX Using Linux, Third Edition

Connecting to UNIX/Linux Using Telnet or SSH Remotely through Telnet Through network client software As peer on peer-to-peer network On a stand-alone PC Through a dumb terminal Guide to UNIX Using Linux, Third Edition

Connecting to UNIX Using Telnet Telnet is terminal emulation software Connects your PC to a server, or host PC could be running UNIX, Linux, Windows OS, or Macintosh OS Once connected to a UNIX/Linux host, work with UNIX/Linux may begin Uses IP addresses or domain names to access remote systems Guide to UNIX Using Linux, Third Edition

Secure Shell (SSH) Developed for UNIX/Linux systems to provide authentication security for TCP/IP applications, such as FTP and Telnet Can encrypt communications as they go across a network or the Internet openSSH includes protocols and software for free distribution on UNIX/Linux systems Guide to UNIX Using Linux, Third Edition

Logging In to UNIX/Linux Log in by entering username and password when UNIX/Linux system booted or connected to Enter at prompt (command-line mode) or into login box (GUI mode) Now commands can be issued at the command prompt Guide to UNIX Using Linux, Third Edition

Logging In to UNIX/Linux (continued) With a standalone computer and an X Window desktop such as GNOME, you must open a terminal window to access the command prompt Guide to UNIX Using Linux, Third Edition

Using Commands To interact with UNIX/Linux, a command is entered at the command prompt UNIX/Linux is case-sensitive and most commands are typed in lower case Two categories of commands User-level: perform tasks System administration: system management Guide to UNIX Using Linux, Third Edition

Using Commands (continued) The date command Displays the system date, which the system administrator maintains The cal command Shows the system calendar Guide to UNIX Using Linux, Third Edition

Using Commands (continued) Guide to UNIX Using Linux, Third Edition

Using Commands (continued) Guide to UNIX Using Linux, Third Edition

Using Commands (continued) The who Command To get information about who is logged in Useful for administrators and users The clear Command Clears the screen The whatis command Displays a brief description of a command for help purposes Guide to UNIX Using Linux, Third Edition

Using Commands (continued) The man program displays the UNIX/Linux online reference manual, called the man pages, for help purposes Guide to UNIX Using Linux, Third Edition

Using Commands (continued) Command-line editing Certain keystrokes perform command-line editing (shell dependent) Multiple command entries More than one command on one line by separating with a semicolon(;) Guide to UNIX Using Linux, Third Edition

Using Commands (continued) Command-line history Use up and down arrow keys to scroll through command history Logging out ends your current process and indicates to UNIX that you are finished Logging out is shell dependent Bourne, Korn, Bash – exit command C shell – logout command Guide to UNIX Using Linux, Third Edition

Understanding the Role of the UNIX/Linux System Administrator System administrator manages the UNIX/Linux system Adds users and deletes old accounts Also called the superuser Unlimited permission to alter system Unique user name: root Prompt ends with # (pound) symbol Guide to UNIX Using Linux, Third Edition

Understanding the Role of the UNIX/Linux System Administrator (continued) The System Administrator’s Command Line [root@hostname root]# The Ordinary User’s Command Line [username@hostname username] $ Guide to UNIX Using Linux, Third Edition

Changing Passwords For security purposes, changing passwords is necessary Use the passwd command UNIX/Linux allows new password if: The new password differs by at least three characters It has six or more characters, including at least two letters and one number It is different from the user name Guide to UNIX Using Linux, Third Edition

Viewing Files Using the cat, more, less, head, and tail Commands Use cat, more, and less to view an entire file contents cat displays a whole file at one time more displays a file one screen at a time, allowing scroll down less displays a file one screen at a time, allowing scroll down and up Guide to UNIX Using Linux, Third Edition

Viewing Files Using the cat, more, less, head, and tail Commands (continued) Use head and tail to view the first few or last few lines of a file head displays the first few lines tail displays the last few lines Guide to UNIX Using Linux, Third Edition

Redirecting Output The greater than sign (>) is called a redirection symbol Create a new file or overwrite an existing file by attaching (>) to a command that produces output To append to an existing file, use two redirection symbols (>>) Guide to UNIX Using Linux, Third Edition

Chapter Summary OS controls all computer resources and provides the base upon which application programs can be used or written A server-based network is centralized (handled by the system administrator) A peer-to-peer network is decentralized UNIX/Linux are multi-user, multitasking Guide to UNIX Using Linux, Third Edition

Chapter Summary (continued) UNIX/Linux systems can be configured as servers, client workstations, client/server workstations, or stand-alone The concept of the layered components that make up an OS originated with UNIX Linux is a UNIX-like OS for a PC You communicate with the OS programs through an interpreter called the shell Guide to UNIX Using Linux, Third Edition

Chapter Summary (continued) The system administrator sets up accounts for users that supply a username and password You work with UNIX by typing commands that you can learn by referring to the online manual called man pages Guide to UNIX Using Linux, Third Edition

Chapter Summary (continued) Most shells provide basic command-line editing capabilities and keep a history of your most recently used commands You can view the contents of files with view commands such as cat, less, more, head, and tails Guide to UNIX Using Linux, Third Edition